Alcohol ingestion is known to greatly increase the frequency and severity of hypoxic events in patients with obstructive sleep apnea (OSA). OSA is a life threatening disorder caused by repetitive narrowing and collapsing of the upper airway during sleep, causing hundreds of brief arousals, sleep deprivation, cardiac arrhythmias, excessive sleepiness and loud snoring; most often in overweight, middle aged and older males. Our long range goals are to identify conditions that foster OSA and identify those at risk of developing or having OSA and hypoxic events that can cause potentially fatal arrhythmias with the objective of reducing the incidence of OSA, developing tests for its early detection and establishment of appropriate preventive measures. Our specific aims are to assess the effects of evening ingestion of alcohol on breathing during sleep, to see if alcohol (about 3-8 oz of 80 proof) can exacerbate or cause hypoxic events due to obstructed breathing during sleep (OBS) or OSA, in 128 males between the ages of 30-69: 32 non-obese normals, 32 healthy non-obese snorers, 32 above 20 percent and 32 above 40 percent ideal weight, with each group split into 16 males 30-49 and 16 males 50-69. A latin square, double blind repeated measures design, 2 X 4 X 4: 2 age groups, 4 risk groups (normals, non-obese snorers, obese and very obese) balanced and randomized for order on 4 treatments (trace, .4, .8, 1.0 gm/kg ethanol mixed with gingerale), will allow a full evaluation of these factors. Respiration will be monitored during sleep by intercostal-EMG, nasal-oral thermocouples and ear oximetry, which will allow us to identify and quantify obstructive breathing and hypoxic events during the 4 experimental polysomnographic sleep studies for each subject. The frequency and severity of hypoxic events due to OBS and OSA following each treatment will be compiled and statistically analyzed using analysis of variance, to assess between-within group/subjects comparisons and interactions. We will also assess the effect of alcohol on each subject's sleep, cardiac rhythms, and snoring loudness. This investigation will allow us to empirically test our hypotheses that alcohol can induce OBS and OSA in normals, non-obese snorers, and those who are significantly overweight, as a function of the quantity of alcohol consumed. The results of this study may be of vital importance to a significant portion of the population.